Apparatus for cooling surfaces

Abstract

In methods and apparatus for cooling surfaces, a pressurized liquid refrigerant is dispensed through a shaped member composed of an open celled foam. The method is particularly useful for localized freezing of a wart or other growth prior to its removal from skin of a human being or another animal.

What is claimed is: 
     
       1. An assembly for dispensing a refrigerant, said assembly comprising (1) a container which (a) includes a valve having an inlet and an outlet, and   (b) is sealed except for the valve;     (2) a liquid refrigerant which (a) is contained under pressure within the container and   (b) has a boiling point at atmospheric pressure of less than 0° C.;     (3) a feed tube which has (a) a first end within the refrigerant, and   (b) a second end which communicates with the inlet of the valve;     (4) an outlet tube which has (a) a first end which communicates with the outlet of the valve, and   (b) a discharge end; and       (5) a dispensing head which (a) comprises a shaped member composed of an open celled foam, and   (b) is secured to the discharge end of the outlet tube so that, when the valve is open, the refrigerant is dispensed through the open celled foam.     
     
     
       2. An assembly according to claim 1 wherein the foam has a density of 10-40 kg/m 3  and a pore size of 20-40 pores/cm. 
     
     
       3. An assembly according to claim 1 wherein the foam is composed of a polyester-based polyurethane. 
     
     
       4. An assembly according to claim 1 wherein the foam has an elongation of 200 to 500% at 20° C. 
     
     
       5. An assembly according to claim 1 wherein the foam has an elongation of 300 to 400% at 20° C. 
     
     
       6. An assembly according to claim 1 wherein the foam is wetted by the refrigerant. 
     
     
       7. An assembly according to claim 1 wherein the shaped foam member is hollow and fits over the discharge end of the outlet tube so that there is a space between the discharge end and the foam. 
     
     
       8. An assembly according to claim 7 wherein at least a part of the space between the discharge end and the foam is filled by a permeable solid material. 
     
     
       9. An assembly according to claim 8 wherein the permeable solid material is cotton wool. 
     
     
       10. An assembly according to claim 7 wherein the space between the outlet tube and the interior surface of the shaped foam member has a volume which is from 15πD 2  /4 to 40πD 2  /4 mm 3 , where D is the external diameter of the outlet tube in mm. 
     
     
       11. An assembly according to claim 7 wherein the wall thickness of the shaped foam member is 3 to 4 mm. 
     
     
       12. As assembly according to claim 7 wherein the internal surface of the shaped foam member defines a cavity having a proximal end portion which is secured to the outlet tube, a center portion which surrounds the end portion of the outlet tube and is spaced apart from the outlet tube, and a distal portion which extends beyond the discharge end of the outlet tube. 
     
     
       13. An assembly according to claim 12 wherein the axial length of the proximal portion is at least 0.75D, the axial length of the center portion is 2D to 10D, and the axial length of the distal portion is at least 0.4D, where D is the external diameter of the outlet tube. 
     
     
       14. An assembly according to claim 13 wherein the length of the proximal portion is 1.5D to 3D, the length of the center portion is 3D to 6D, and the length of the distal portion is 0.5D to 2D. 
     
     
       15. An assembly according to claim 13 wherein the outlet tube has an external diameter of 2 to 4 mm and a wall thickness of 0.15 to 0.4 mm. 
     
     
       16. An assembly according to claim 12 wherein the axial length of the proximal portion is 2 to 12 mm, the axial length of the center portion is 3 to 18 mm, and the axial length of the distal portion is 1.5 to 8 mm. 
     
     
       17. An assembly according to claim 16 wherein the length of the proximal portion is 3 to 8 mm, the length of the center portion is 6 to 15 mm, and the length of the distal portion is 2 to 6 mm. 
     
     
       18. An assembly according to claim 16 wherein the space between the outlet tube and the interior surface of the shaped foam member has a volume of 60 to 200 mm 3 . 
     
     
       19. A method of cooling the skin of a living mammal, said method comprising (1) placing adjacent to the skin the dispensing head of an assembly as claimed in claim 1, and   (2) opening the valve of said assembly so that refrigerant in the container of said assembly passes through the feed tube, the outlet tube and the open celled foam of the dispensing head of said assembly and evaporates adjacent to the skin.   
     
     
       20. A method according to claim 19 wherein the living mammal is a human being. 
     
     
       21. A method according to claim 20 wherein the skin which is cooled comprises a wart. 
     
     
       22. An assembly for dispensing a refrigerant, said assembly comprising (1) a container which (a) includes a valve having an inlet and an outlet, and   (b) is sealed except for the valve;     (2) a liquid refrigerant which (a) is contained under pressure within the container and   (b) has a boiling point at atmospheric pressure of less than 0° C.;     (3) a feed tube which has (a) a first end within the refrigerant, and   (b) a second end which communicates with the inlet of the valve;     (4) an outlet tube which has (a) a first end which communicates with the outlet of the valve, and   (b) a discharge end; and       (5) a dispensing head which (a) comprises a shaped member composed of an open celled foam which (i) has a density of 10-40 kg/m 3 ,   (ii) has a pore size of 20-40 pores/cm, and   (iii) is composed of a polyester-based polyurethane and       (b) is secured to the discharge end of the outlet tube so that, when the valve is open, the refrigerant is dispensed through the open celled foam.     
     
     
       23. A method of cooling the skin of a human being, said method comprising (1) placing adjacent to the skin the dispensing head of an assembly as claimed in claim 22, and   (2) opening the valve of said assembly so that the refrigerant in the container of said assembly passes through the outlet tube and the open celled foam of the dispensing head of said assembly and evaporates adjacent to the skin.